Substation circuit



Dec. 13, 1927.

' W. G. SHULL SUBSTATION CIRCUIT Filed Dec. 20. 1920 517642701 M/[ram 52111] Patented Dec. 13, 1927.

UNITED STATES PATENT OFFICE.

WILLIAM SHULL, OF CHICAGO, ILLINOIS,

ASSIGNOR 'I'O KELLOGG SWITCHBOARD AND SUPPLY COMPANY, OF CHICAGO,ILLINOIS, A CORPORATION OF ILLINOIS.

SUBSTATION CIRCUIT.

Application filed December 20, 1920. Serial No. 431,859.

My invention relates in general to substation telephone circuits, but ismore particu larly directed to substation circuits for use in connectionwith automatic telephone systems, and an object of my invention is theprovision of a substation circuit as above outlined, having an improvedand simplified arrangement, positive and eflicient in its operation.

A feature of my invention is the provision of means in the substationcircuit whereby the receiver is shunted while the impulse transmitter isfunctioning and the secondary winding of the induction coil placedacross the line conductors so that upon each interruption of the impulsesprings discharge current from the secondary winding of the inductioncoil flows back over the telephone line in a direction opposite to thatof the initial flow of current in the line circuit. The flow ofdischarge current being in a direction to neutralize the magnetism ofthe controlling relay of the automatic apparatus at the exchange, itresults that each time the impulse springs of the substation circuit areinterrupted a snap release of the said cont-rolling relay is producedand any lag of the controlling circuit of the automatic apparatus at theexchange is overcome.

The novel features above outlined and the further features of myinvention not specifically referred to above will appear from'thedetailed description taken in connection with the accompanying drawings,in which a preferred embodiment is illustrated.

In the drawing I show the transmitter T and the winding 2 of theinduction coil 10 connected across the line conductors 3 and 4 while thereceiver R is in a circuit with the condenser C and the other winding 5of the induction coil IO. The circuit of the transmitter T and receiverR are normally open when the receiver R is on the switchhook H, andclosed when the receiver R is removed. The circuit of the transmitter Tincludes the switchhook controlled contacts 6 and 7 and the circuit ofthe receiver R includes the switchhook controlled contacts 8 and 9. Asignaling circuit compris ng a call bell CB and condenser C areconnected across the line conductors 3 and 4, but are not under thecontrol of the receiver switchhook H. The subscribers impulse sender orcalling device indicated by the reference character CD may be of anyapproved type known in-the art, or such as illustrated and described inan application filed by Harry H. Ide, April 9, 1920, -and bearing SerialNo. 372,525. It comprises springs 10 and 11 controlled by a suitablerotatable cam through the medium of a finger hold actuatmg member andgearing. Shunt springs SS are also provided and comprise spring contactmembers 12, 13 and 14; which are closed whenever the finger holdactuating member of the calling device CD is rotated from its normalposition. The impulse springs 10 and 11 are included in series with theline conductor 4 and their function is to produce momentaryinterruptions of the line circuit for the purpose of operating thecentral office switching devices in the manner well known in the art.The shunt springs 12, 13 and 14, when closed, short circuit the receiver.R and transmitter circuits in order to reduce the resistance of theline circuit and to prevent the interruptions of the line circuit due tothe opening and closing, of the impulse springs 10 and 11 being heard inthe receiver. The mechanics of such a device are so well known that anyparticular description thereof would be superfluous.

Having described in general the apparatus embodying my invention, adetailed description of its operation will now be given, and for anexample of a suitable central oflice arrangement, reference is made topatent to Harry H. Ide issued August 15, 1916, No. 1,194,741.

Upon removal of receiver R to initiate a call, the switchhook controlledcontacts 6 and 8 come into engagement, respectively, with the contactsprings 7 and 9, whereby the circuit of the transmitter T and thecircuit of the receiver R are closed. Responsive to the closure of thetransmitter circuit, current is supplied to the transmitter from thebattery bridged at the central exchange over the following path: overline conductor 3, winding 2 of the induction coil IC, transmitter T,contacts 10 and 11, closed switchhook contacts 6 and 7, to the lineconductor 4. The bridge at the central oflice which includes the batterymay also, in accordance with the usual practice, include the ContrOllingor impulse relay of the automatic switch, the circuit of the saidimpulse relay including, therefore, the transmitter at the substation.The calling subscriber may, by

suitably manipulating his calling device finger-hold actuating'member,produce a series of interruptions in the circuit of the controlling orimpulse relay to bring about the operation of the switch associated withsaid relay. As soon as the finger-hold actuating member is turned fromits normal position, the substation circuit is completed over a new pathtraced from line conductor 3, winding 2 of the induction coil TC,conductors 15 and 16, closed shunt springs 13 and 14, conductors 17 and18, closed contacts 10 and 11 of the impulse springs IS, conductor 19,closed contacts 6 and 7 of the substation switchhook E to conductor 4.The closure of springs 12 and 13 shunts the receiver R, and closure ofshunt springs 13 and 14 shunts the transmitter T for the purposes asalready described. Successive operations of the dial will now result inthe operation of successive switches at the exchange until theconnection is finally completed to the line of the called subscriber. 7

When the finger-hold actuating member is turned from normal and theshunt springs 12, 13 and 14 are closed and the substation loop isextended from the line conductor 3 over the path just described to theconductor 4, current flows through the winding 2 of the induction coil10 and upon each momentary interruption of the impulse springs 10 and 11as the finger actuating member returns to normal, this circuit or loopis opened and closed to bring about the deenergization and energizationof the controlling relay at the exchange. At the instant that theimpulse springs 10 and 11 are interrupted, the current flow through thewinding 2 of the induction coil IC ceasesand the magnetic field aboutthe winding 2 collapses andinduced current from the secondary winding 5of the induction coil 10 discharges into the telephone line in theopposite direction to that in which current was fiowing through thewinding 2 and the telephone line when the substation loop wasinterrupted. The condenser C and winding 5 of the induction coil 16 areconnected as follows when the actuating member is off normal: from lineconductor 4, condenser C, winding 5 of the induction coil TC, closedswitchhook controlled contacts 8 and 9, closed shunt springs 12 and 13,conductors 16 and 15, winding 2 of the induction coil IC to the lineconductor 3. This circuit just traced connects the condenser C andwinding 5 of the induction coil IC across the line conductors and theinduced current from the winding 5 (in the opposite direction to theflow of current in the line circuit) decreases the reluctance ot thecircuit of the impulse relay of the switch at the exchange. This givesthe impulse relay a snap release the instant the impulse springs 10 and11 are interrupt-- ed, thereby producing a positive de-energization ofthe impulse relay and a positive actuation of the switch associated withthe impulse relay.

While I have illustrated and described a preferred embodiment of myinvention, 1 do not wish to be limited to the exact structure shown aschanges and modifications will readily suggest themselves and I,therefore, aim to cover all such changes and modifications as comewithin the spirit and scope of the appended claims. 7

What I claim as'new and desire to secure by Letters Patent, is:

l. A telephone system including a substation provided with a transmitterand a receiver, a substation controlled contact an impulse transmitterwith impulse springs and having ottnormal contacts for short-circuitingsaid transmitter and receiver when the impulses are being sent, saidimpulsing circuit including said first contact, a repeating coil havinga winding connected to the line limbs and included in the impulsetransmitting circuit at the substation, and a branch circuit, includinga condenser and the other windingot the repeating coil, shunting theimpulse springs.

2. A telephone system including a substation provided with a transmitterand receiver, an impulse transmitter having olinormal contacts tooperatively, disassociate said transmitter and receiver of thesubstation from the impulse transmitting circuit only when said receiveris removed from its switchhook, one winding of an induction coilincluded in said circuit, impulse springs in said circuit, said springswhile transmitting impulses being shunted by a branch includingthe otherwinding of the induction coil, said b "anch being'opaque to steadycurrent but transparent to varying current.

3. An impulse transmitting circuit for automatic exchanges including aninduction coil, normally open substation v receiver switchhookcontacts,impulse contacts directly conductively connected with one winding ofsaid induct-ion coil only when said normally open switchhook contactsareclosed, the other winding of said coil shunting said contacts whilethe impulses are being transmitted.

. 4. A transmitting station for automatic exchanges including atelephone transmitter and a receiver, an induction coil, animpulsesender including impulse contacts connectedwith one winding ofsaid induction coil, a hookswitch contact, oil-normal means of saidsender to operatively remove said transmitter from connection with theimpulse transmitting circuit, said transmitting circuit including saidhookswitch contact. the other winding of" said induction coil shuntingsaid contacts while the impulses are being transmitted. I

6. An impulse transmitting station for automatic exchanges including atelephone receiver, an induction coil, an impulse sender includingimpulse contacts connected with one winding of said induction coil, theother winding of said induction coil shunting said contacts whileimpulses are being transmitted and only when said receiver is removedfrom its switchhook, and off-normal means of said sender to operativelydissociate said receiver from the impulse transmitting circuit.

6. An impulse transmitting station for automatic exchanges connected toa telephone line including an impulse sender, an induction coil havingone of its windings connected across said line, another winding of saidcoil and a condenser connected across said line while impulses are beingtransmitted, an impulse transmitting contact in a portion of said linein shunt of said second winding, a receiver and transmitter for saidstation and a switch comprised in said sender for altering the circuitsof said receiver and transmitter only when said receiver is removed fromits switchhook to permit said switchhook to close normally open contactsin said telephone line.

7. A transmitting station for automatic exchanges including an impulsesender connected to a telephone line, normally open contacts in saidline, a substation receiver switchhook for closing said normally opencontacts, two windings of an induction coil and a condenser in seriesconnection with a limb of said line, a conductive shunt extending aboutthe condenser and one winding, and the impulse transmitting contact ofsaid sender connected in said shunt only when said normally opencontacts are closed by said receiver switchhook.

8. A transmitting station for automatic exchanges including an impulsesender connected to a telephone line, two windings of an induction coiland a condenser in series with a limb of said line, a conductive shuntextending about the condenser and one of said windings, the impulsetransmitting contact of said sender connected in said shunt, atransmitter and receiver for said substation and a switch automaticallyactuated while the sender is working to operatively exclude saidtransmitter and receiver only when said receiver is removed from itsswitchhook.

9. A sending station for automatic exchanges including an impulse senderconnected to a line and adapted to be traversed by current over saidline, a receiver and a transmitter :for said station, an impulse contactand means for opening and closing it to transmit the impulses, and aninduction coil having its one winding in circuit with said contact andits other winding in shunt circuit of said contact only when saidreceiver is removed from its switch hook for discharging current by eachopening of said contact against the previous current 1n the line.

10. A sending station for automatic exchanges including an impulsesender connected to a line and adapted to receive current thereover, areceiver and a transmitter for said station, an impulse contact andmeans for opening and closing it to transmit the impulses, a winding anda condenser connected in a shunt about said contact, a sec ond windingconnected with said contact and outside said shunt and adapted onclosure of said contact to charge said first winding only when saidreceiver is removed from its switchhook, the subsequent opening of saidcontact serving to discharge said first winding against the direction ofthe previous current in the line.

11. A transmitting station for automatic exchanges including an impulsesender, a telephone transmitter and an off-normal contact closed whenthe sender is operated to short-circuit it, a telephone receiver and asecond off-normal contact, said last contact closed when the sender isoperated to shortcircuit said receiver only when said receiver is movedfrom its switchhook, an impulse spring of said sender connected to saidfirst contact, the other impulse spring being in connection with aswitchhook contact, another switch hook contact connected to said secondoff-normal contact and said receiver, an induction coil having a windingconnected to the transmitter, a condenser adapted to be connected withsaid receiver by the operation of the switchhook, the other winding ofsaid induction coil being connected between said hook and saidcondenser. said switchhook contacts and said off-normal contacts jointlycontrolling the talking and impulse sending circuits.

12. In a telephone system including a substation provided with impulsesending contacts, a receiver and a transmitter for said substation, aninduction coil having its one winding in circuit with said impulsesending contacts and its other winding in shunt circuit of saidcontacts, said shunt circuit including a switchhook contact,arelabridged across the line limbs of said telephone sys tem, and means foroperating said contacts to open the circuit of said first winding tocause current to be induced in said first winding by said shunt windingto effect a positive snap action of said relay.

13. In a telephone system including a substation provided with impulsecontacts, a receiver and a transmitter for said substation, an inductioncoil having its one winding in circuit with said impulse contacts andthe other winding in shunt circuit of said contacts, said shunt circuitincluding a pair of contacts controlled by the substation switchhook, animpulse relay bridged of said-telephone system, andineans for operatingsaid device to afiect the windings of said induction coil whereby aquick action of said relay is effected, the impulsing circuit for saidrelay including a pair of normally opened contacts closed only Whensaidsubstation is in use. 7

Signed by me at Chicago, in the county of Cook and State of Illinois,this 18th day of December, 1920.

WILLIAM G. SHULL.

